A design consideration of vehicular headlamp systems concerns maximum and minimum illumination levels and produced beam patterns. In addition to this concern, aesthetic and physical design factors also play a role in the design of headlamps. Conventional incandescent and gas discharge headlamp systems have required a relatively large volume for their components, limiting the ability to design and implement more compact headlamp systems. Accordingly, it has been suggested to employ semiconductor light sources in headlamp systems as light sources.
While recent advances in the manufacture and/or design of semiconductor light sources have resulted in light sources, such as white LEDs, achieving relatively high light output levels, multiple semiconductor light sources must still be employed in a headlamp system to obtain the required levels of light output for a headlamp. Further, semiconductor sources introduce new design challenges to headlamp systems. For example, semiconductor light sources act much more like ideal point sources of light than incandescent and/or gas discharge bulbs and thus conventional headlamp optical designs may not be compatible with semiconductor light sources. In addition, issues such as the need to provide the necessary cooling of semiconductor light sources further complicate the design of headlamp systems employing semiconductor light sources.
Another long felt need in the area of vehicular headlamps is the ability to illuminate the area of the road where the vehicle is going to travel, rather than (or in addition to) the area of the road in front of the vehicle. Previous attempts have been made to provide steerable headlamps to address this issue and most of these prior art systems have included mechanical means to physically turn the headlamp, or a portion of the optics (such as a reflector and/or lens) in the headlamp, with the front wheels of the vehicle to direct the illumination from the headlamp in the desired direction. A variety of techniques have been attempted for the control of steerable headlamps, ranging from mechanical linkages with the steering mechanism of the vehicle to microprocessor controlled servo-motor driven systems.
However, such systems suffer from disadvantages in that the control mechanisms to turn the headlamp can be quite complex, expensive and/or fragile. Other prior art systems have included an additional light source in each headlamp, the left headlamp having an additional light source to illuminate the area to the left of the car and the right headlamp having an additional light source to illuminate the area to the right of the car and these additional light sources are turned on or off, appropriately, as the front wheels of the vehicle are turned. These systems also suffer from disadvantages as the area illuminated by the additional light sources is fixed and does not change with the vehicle speed or turn angle and thus the resulting beam pattern may not provide the desired illumination.
Accordingly, there exists a need for new and improved vehicular headlamp systems whose desired beam patterns are formed from light emitted by semiconductor light sources.